RESUMEN
OBJECTIVE: The study aims were to demonstrate apoptosis in the placenta of normal pregnancy, and to identify its change and quantify its incidence by gestational age. METHODS: Placenta samples were collected from 25 normal full-term pregnancies and 20 second trimester pregnancies undergoing termination due to medical and social reasons. Hematoxylin and eosin staining and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling) staining were used to quantify the incidence of apoptosis and the electron microscopy was used to confirm it. Mann-Whitney U test and ANOVA test were used for statistical analysis. RESULTS: 1. Apoptosis was demonstrated by variable cytopathologic methods, and especially TUNEL staining and electron microscopy are found to be confirmatory methods. 2. In TUNEL staining, quantification of apoptosis was as follows: 2nd trimester (n=20) 1.05+/-0.69, full- term (n=25) 1.92+/-1.00. The incidence of apoptosis was significantly higher in full-term than in 2nd trimester (p0.05, Mann-Whitney U test). 4. There was no statistical significance in the incidence of apoptosis by maternal age, parity, cause of termination during 2nd trimester, and mode of delivery in each group. 5. In the electron microscopy, apoptotic cells were observed to have membrane blebbing, loss of microvilli, chromatin condensation and localization in the border of nuclear membrane, and cell shrinkage and increase in granularity. This method was conformatory in identifying apoptosis. CONCLUSION: Placental apoptosis increased significantly with increased gestational age, and this result suggests that it may play a role in the normal development and aging of the placenta.